according to the vendor, what exactly would be the root cause of the problem ?
please let me know about your dtx experiments, it did fix AMR issues related to poor RxQual in ALU networks.
the FDR solution is usually used the other way around. Basically I would have a totally different approach than yours 🙂 Here is my strategy :
– call setup in 1800 rather than 900 (thanks to CRO)
– if 1800 is full, then we are happy, and we use FDR to direct excess voice traffic to 900
– if it is a GPRS TBF that is setup, then it should be redirected immediately to 900 cell (even if 1800 is not full). This can be done with specific NC2 parameters tuning.
Now, with your approach, a TCH HO makes more sense than FDR. I cannot say there are drawbacks with your method, except perhaps:
– allocating 2 TCHs for one call (one in the 900, another one in the 1800). Even if the 1st TCH is quickly deallocated, it still means there is a little waste here.
– when 1800 is congested, the 900 will still detect the HO cause, leading to poor outgoing HO congestion rate. Not impacting the subscribers though, so not really important.
– you are dedicated one HO cause for this specific purpose, therefore it cant’ be used for something else.
– your SDCCH radio quality depends on your 900MHz freq plan. Usually not that great… so perhaps you have higher SD drop rate and higher SD assign fails than you could.
What do you think ? I’d like to hear your opinion 🙂